The invention relates generally to antennas, and more particularly, to phased array antennas.
Phased array antennas have had wide application to many systems including radar systems. Antenna beams may be steered rapidly through a wide range of angles and mechanical rotation of the antenna, while it is an effective technique, is not necessary in many applications because of the scanning capabilities of phased array antennas. By controlling the phased array antenna with a computer, high scanning and data rates are possible and the antenna is able to simultaneously perform multiple, interlaced functions such as fire-control, surveillance, tracking and communications. A computer controlled phased array antenna is also capable of interacting with multiple targets simultaneously under a variety of conditions and its time allocation to particular targets can be adjusted to optimize performance in the particular application.
However phased array antennas have one well known disadvantage their expense. Due to this expense, which is typically very large, they are not used in many applications where they would be the best choice based on performance characteristics.
One of the most expensive parts of the phased array antenna is the phase shifter. In many prior techniques, each radiating element has its own phase shifter feeding it. In the case where a narrow antenna beam is desired, thousands of radiating elements are used and so thousands of accompanying phase shifters with control drivers are required. Not only is the expense of the individual phase shifter substantial, but the expense associated with installing, testing, and controlling each phase shifter is also large. Where hemispherical coverage is necessary and a mechanically rotating antenna is not desired, four phased array apertures or faces may be used. These four apertures result in a four-fold increase in the number of phase shifters in many prior techniques. In most cases, this would result in a prohibitively high cost not only in terms of component cost, but also in terms of labor costs for installation, alignment, and service of such a large number of components, and because of that cost, a phased array antenna would not be used.
Accordingly, it would be an advance in the art to provide a phased array antenna capable of hemispherical scan coverage without mechanical rotation but which uses fewer phase shifters than prior techniques and has substantially the same performance.
It is an object of the invention to provide an improved phased array antenna.
It is a further object of the invention to provide a phased array antenna capable of hemispherical scan coverage without using mechanical rotation and which uses fewer than one phase shifter per radiating element.
It is a further object of the invention to provide a phased array antenna capable of simultaneous hemispherical coverage without mechanical rotation and using fewer phase shifters than prior techniques.
It is a further object of the invention to provide a phased array antenna providing hemispherical scan coverage by means of four stationary apertures with sets of one radiating element from each aperture interconnected with a single phase shifter, and maintaining substantially the same performance as that of an antenna having four faces with one phase shifter per each radiating element.
It is a further object of the invention to provide a phased array antenna capable of simultaneous hemispherical coverage without mechanical rotation and using fewer phase shifters than prior techniques and which is adaptable to disposing transmit and receive components at the antenna aperture for functioning as a solid state array.
It is a further object of the invention to provide a phased array antenna capable of providing hemispherical scan coverage by means of four stationary apertures with sets of one radiating element from each aperture interconnected with a single phase shifter, and which is capable of simultaneously generating multiple beams from a single aperture.